This invention relates to remote controlled load actuating systems. More particularly, it involves a combination automatic garage door operator and home security system.
Remote actuation of garage door operators and similar loads have been accomplished traditionally by means of a radio control system wherein transmitters and receivers are matched to one another by frequency selection. An inherent disadvantage of this approach is the limited number of available carrier frequencies and the possibility of a match between transmitters and receivers belonging to different persons.
With an increasing awareness of such a potential security problem, the recent trend in providing remotely actuated garage door operators is to provide the owner with the capability of selecting his own personalized code in the transmitter and receiver sections. Many of the recent systems employ digital coding techniques in which the owner selects a particular combination of switches to set the code. Representative examples of known garage door operator systems are disclosed in U.S. Pat. No. 4,141,010 to Umpleby et al; U.S. Pat. No. 3,906,348 to Wilmott; and U.S. Pat. No. 4,037,201 to Wilmott. U.S. Pat. No. 4,141,010 and U.S. Ser. No. 15,495 are hereby incorporated by reference.
It is of course well known that internal combustion engines such as those used in automobiles generate carbon monoxide gas. Carbon monoxide gas is poisonous and high levels of this gas can lead to serious injury and even death if consumed by human beings and animals. Several attempts have been made to monitor the presence of toxic gas and provide warning signals when a dangerous level has been reached. U.S. Pat. No. 3,418,914 to Finken discloses an automobile ventilation technique in which a temperature responsive impedence bridge compares the thermal conductivity of cabin atmosphere with that of a reference environment in order to monitor the cabin for abnormal carbon dioxide concentrations. The output signal from the bridge is used to activate a warning device and/or a ventilating system. U.S. Pat. No. 3,826,180 to Hayashi similarly discloses a ventilator wherein an electronic circuit is actuated when a detecting element senses the existence of smoke or gas, with a fan being automatically actuated to expell the smoke or gas from the environment.
None of the prior art, however, suggests the utilization of a toxic gas sensor in combination with an automatic garage door operator, such that the garage door is automatically opened when a dangerous level of toxic gas is detected. More importantly, the unique environmental conditions that are experienced in normal use of a garage makes the utilization of prior art sensing circuitry impractical. For example, a certain amount of toxic gas is generated when the automobile is initially started up in the garage. Once the user has backed out of the garage and shut the door, the sensor may be activated due to the increased concentration of the toxic gas. This may result in the undersirable opening of the garage door after the user has left the premises, thereby opening the way for unwanted intruders.
Home security systems utilizing burglar alarms have gained increasing popularity in recent years. They generally employ switches or other detector devices to monitor the position of building entrances such as doors and windows. When the alarm system is set, the tripping of the switches will energize a warning device. Unfortunately, the alarm system must be actuated or set locally, primarily by throwing a switch on the control unit located within the building. Accordingly, there is no convenient way of sensing the unauthorized instrusion into the building via the garage door since the burglar alarm must be set before leaving the premises. If the garage door was monitored by such alarm systems, the opening of the garage door so that the user could leave the garage would set off the warning devices.